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Re: Avoid backtrace tests matching filenames when searching forfunction names


On Wed, 23 Jan 2013, Roland McGrath wrote:

> You could put some other repeated bits into the shared header file,
> such as the NO_INLINE and FAIL macros.

Done in this version.

> What's the reason for putting NO_INLINE on do_test?

Generally trying to control what the sequence of functions should look 
like as much as possible, even though in fact it's not possible to get a 
name for do_test in the backtrace, so the testing stops before there.

> Make the function return bool since its only callers are testing its result
> only as a Boolean.  Don't use implicit coercion to Boolean in the function.
> The explanation of what kind of matching it does and the rationale for that
> belongs in the comment on the function itself, not just in the posting.

Done in this version.

> The matching is technically still not robust.  The file name could contain
> a '('.  Robust matching would look back from the last ')' or something like

The glibc build system - and most makefiles in general - wouldn't work in 
practice if the paths to either source or build trees contained a '(' or 
other characters with special meaning to the shell.

The function names being tested for all involve non-hex characters so 
cannot accidentally match hex offsets, and this is explicitly referred to 
in the new comment.

2013-01-23  Joseph Myers  <joseph@codesourcery.com>

	* debug/tst-backtrace.h: New file.
	* debug/tst-backtrace2.c: Include tst-backtrace.h.
	(ret): Remove variable.
	(x): Likewise.
	(FAIL): Remove macro.
	(NO_INLINE): Likewise.
	(fn1): Use match function instead of strstr.
	* debug/tst-backtrace3.c: Include tst-backtrace.h.
	(ret): Remove variable.
	(x): Likewise.
	(FAIL): Remove macro.
	(NO_INLINE): Likewise.
	(fn): Use match function instead of strstr.
	* debug/tst-backtrace4.c: Include tst-backtrace.h.
	(ret): Remove variable.
	(x): Likewise.
	(FAIL): Remove macro.
	(NO_INLINE): Likewise.
	(handle_signal): Use match function instead of strstr.
	* debug/tst-backtrace5.c: Include tst-backtrace.h.
	(ret): Remove variable.
	(x): Likewise.
	(FAIL): Remove macro.
	(NO_INLINE): Likewise.
	(handle_signal): Use match function instead of strstr.

diff --git a/debug/tst-backtrace.h b/debug/tst-backtrace.h
new file mode 100644
index 0000000..b6fd46a
--- /dev/null
+++ b/debug/tst-backtrace.h
@@ -0,0 +1,51 @@
+/* Test backtrace and backtrace_symbols: common code for examining
+   backtraces.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Set to a non-zero value if the test fails.  */
+volatile int ret;
+
+/* Accesses to X are used to prevent optimization.  */
+volatile int x;
+
+/* Called if the test fails.  */
+#define FAIL() \
+  do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
+
+/* Use this attribute to prevent inlining, so that all expected frames
+   are present.  */
+#define NO_INLINE __attribute__ ((noinline))
+
+/* Look for a match in SYM from backtrace_symbols to NAME, a fragment
+   of a function name.  Ignore the filename before '(', but presume
+   that the function names are chosen so they cannot accidentally
+   match the hex offset before the closing ')'. */
+
+static inline bool
+match (const char *sym, const char *name)
+{
+  char *p = strchr (sym, '(');
+  if (p)
+    return strstr (p, name) != NULL;
+  else
+    return false;
+}
diff --git a/debug/tst-backtrace2.c b/debug/tst-backtrace2.c
index e1d4572..1bdef0d 100644
--- a/debug/tst-backtrace2.c
+++ b/debug/tst-backtrace2.c
@@ -22,27 +22,15 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "tst-backtrace.h"
+
 static int do_test (void);
 #define TEST_FUNCTION do_test ()
 #include "../test-skeleton.c"
 
-/* Set to a non-zero value if the test fails.  */
-int ret;
-
-/* Accesses to X are used to prevent optimization.  */
-volatile int x;
-
-/* Called if the test fails.  */
-#define FAIL() \
-  do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
-
 /* The backtrace should include at least f1, f2, f3, and do_test.  */
 #define NUM_FUNCTIONS 4
 
-/* Use this attribute to prevent inlining, so that all expected frames
-   are present.  */
-#define NO_INLINE __attribute__ ((noinline))
-
 NO_INLINE void
 fn1 (void)
 {
@@ -71,14 +59,14 @@ fn1 (void)
   for (i = 0; i < n; ++i)
     printf ("Function %d: %s\n", i, symbols[i]);
   /* Check that the function names obtained are accurate.  */
-  if (strstr (symbols[0], "fn1") == NULL)
+  if (!match (symbols[0], "fn1"))
     {
       FAIL ();
       return;
     }
   /* Symbol names are not available for static functions, so we do not
      check f2.  */
-  if (strstr (symbols[2], "fn3") == NULL)
+  if (!match (symbols[2], "fn3"))
     {
       FAIL ();
       return;
diff --git a/debug/tst-backtrace3.c b/debug/tst-backtrace3.c
index 4d3309b..182f423 100644
--- a/debug/tst-backtrace3.c
+++ b/debug/tst-backtrace3.c
@@ -22,27 +22,15 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "tst-backtrace.h"
+
 static int do_test (void);
 #define TEST_FUNCTION do_test ()
 #include "../test-skeleton.c"
 
-/* Set to a non-zero value if the test fails.  */
-int ret;
-
-/* Accesses to X are used to prevent optimization.  */
-volatile int x;
-
-/* Called if the test fails.  */
-#define FAIL() \
-  do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
-
 /* The backtrace should include at least 3 * fn, and do_test.  */
 #define NUM_FUNCTIONS 4
 
-/* Use this attribute to prevent inlining, so that all expected frames
-   are present.  */
-#define NO_INLINE __attribute__ ((noinline))
-
 NO_INLINE int
 fn (int c)
 {
@@ -77,7 +65,7 @@ fn (int c)
     printf ("Function %d: %s\n", i, symbols[i]);
   /* Check that the function names obtained are accurate.  */
   for (i = 0; i < n - 1; ++i)
-    if (strstr (symbols[i], "fn") == NULL)
+    if (!match (symbols[i], "fn"))
       {
 	FAIL ();
 	return 1;
diff --git a/debug/tst-backtrace4.c b/debug/tst-backtrace4.c
index 41a3f51..9c0c2a2 100644
--- a/debug/tst-backtrace4.c
+++ b/debug/tst-backtrace4.c
@@ -25,28 +25,16 @@
 #include <signal.h>
 #include <unistd.h>
 
+#include "tst-backtrace.h"
+
 static int do_test (void);
 #define TEST_FUNCTION do_test ()
 #include "../test-skeleton.c"
 
-/* Set to a non-zero value if the test fails.  */
-volatile int ret;
-
-/* Accesses to X are used to prevent optimization.  */
-volatile int x;
-
-/* Called if the test fails.  */
-#define FAIL() \
-  do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
-
 /* The backtrace should include at least handle_signal, a signal
    trampoline, 3 * fn, and do_test.  */
 #define NUM_FUNCTIONS 6
 
-/* Use this attribute to prevent inlining, so that all expected frames
-   are present.  */
-#define NO_INLINE __attribute__ ((noinline))
-
 volatile int sig_handled = 0;
 
 void
@@ -79,14 +67,14 @@ handle_signal (int signum)
   for (i = 0; i < n; ++i)
     printf ("Function %d: %s\n", i, symbols[i]);
   /* Check that the function names obtained are accurate.  */
-  if (strstr (symbols[0], "handle_signal") == NULL)
+  if (!match (symbols[0], "handle_signal"))
     {
       FAIL ();
       return;
     }
   /* Do not check name for signal trampoline.  */
   for (i = 2; i < n - 1; i++)
-    if (strstr (symbols[i], "fn") == NULL)
+    if (!match (symbols[i], "fn"))
       {
 	FAIL ();
 	return;
diff --git a/debug/tst-backtrace5.c b/debug/tst-backtrace5.c
index eb16c23..ca47437 100644
--- a/debug/tst-backtrace5.c
+++ b/debug/tst-backtrace5.c
@@ -26,28 +26,16 @@
 #include <signal.h>
 #include <unistd.h>
 
+#include "tst-backtrace.h"
+
 static int do_test (void);
 #define TEST_FUNCTION do_test ()
 #include "../test-skeleton.c"
 
-/* Set to a non-zero value if the test fails.  */
-volatile int ret;
-
-/* Accesses to X are used to prevent optimization.  */
-volatile int x;
-
-/* Called if the test fails.  */
-#define FAIL() \
-  do { printf ("Failure on line %d\n", __LINE__); ret = 1; } while (0)
-
 /* The backtrace should include at least handle_signal, a signal
    trampoline, read, 3 * fn, and do_test.  */
 #define NUM_FUNCTIONS 7
 
-/* Use this attribute to prevent inlining, so that all expected frames
-   are present.  */
-#define NO_INLINE __attribute__ ((noinline))
-
 void
 handle_signal (int signum)
 {
@@ -76,24 +64,24 @@ handle_signal (int signum)
   for (i = 0; i < n; ++i)
     printf ("Function %d: %s\n", i, symbols[i]);
   /* Check that the function names obtained are accurate.  */
-  if (strstr (symbols[0], "handle_signal") == NULL)
+  if (!match (symbols[0], "handle_signal"))
     {
       FAIL ();
       return;
     }
   /* Do not check name for signal trampoline.  */
   i = 2;
-  if (strstr (symbols[i++], "read") == NULL)
+  if (!match (symbols[i++], "read"))
     {
       /* Perhaps symbols[2] is __kernel_vsyscall?  */
-      if (strstr (symbols[i++], "read") == NULL)
+      if (!match (symbols[i++], "read"))
 	{
 	  FAIL ();
 	  return;
 	}
     }
   for (; i < n - 1; i++)
-    if (strstr (symbols[i], "fn") == NULL)
+    if (!match (symbols[i], "fn"))
       {
 	FAIL ();
 	return;

-- 
Joseph S. Myers
joseph@codesourcery.com


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